SOT (Shale Oil Technology)

ABSTRACT

The proven success of this oil shale technology, including demonstration of the quality of its product, points to the feasibility of the commercial plants&#39; technical functions. This retort system/refinery delivers a higher yield of crude oil and petroleum products both in terms of quantity and quality, utilizing a price conscious and environmentally compatible methodology.

THE PROCESS

The direct heated retort's most important characteristics are its: low-maintenance, moving-bed, gravity-feed system; energy self-sufficiency through combustion of residual carbon in the moving shale particles; unique thermal exchange between descending shale and ascending recycle gas and air/recycle-gas streams; and minimal use of moving parts. The moving bed controls both the intake of raw shale at the top and the discharge of retorted shale at the bottom. A description of the retorting process follows:

RAW SHALE

Crushed shale is fed into the top of the retort where, as a moving bed, it begins its journey downward through four barrier-free but strictly functional areas known as mist-formation, retorting, combustion, and cooling zones. As the shale descends it engages in an efficient heat exchange with a countercurrent flow of recycle gas and air/recycle-gas streams, which are introduced into the retort at different levels by three specific-purpose gas and air/gas distributors.

Oil Mist

Cool off-gas carrying crude shale oil as a suspended mist is collected at the top of the retort and is piped to the oil/gas recovery system. The off-gas is a product of the retorting that takes place when the descending shale encounters kerogen-pyrolizing temperatures in the retorting zone. A carbonaceous residue which remains on the shale in the retorting zones becomes a fuel when the shale bed descends into the combustion zone; where combustion is achieved by the injection of air diluted with recycle gas which is injected into the bottom of the shale bed by the bottom gas distributor. Cooled retorted shale is discharged at the bottom through hydraulically operated grate mechanisms, which regulate the rate and uniformity of the shale's descent through the retort. Displaced shale drops into a collection hopper and passes through a rotary seal and out of the retort enroute to the retorted-shale disposal site.

The ability of the retort to control the bed movement with the discharge-grate system and to control gas distribution and combustion with the multiple-level injection system makes it possible to control heat-release rate and maximum internal gas temperature. Control of gas temperatures improves the quality of the off-gas stream, lowers the heat requirements for retorting, and increases the physical strength of the retorted shale. Lower heat requirements decrease air needs; this results in a decrease in nitrogen dilution in the product gas.

Crude Oil Extraction—Preheating & Mist Formation, Pyrolysis and Combustion

The oil extracted from the shale is released as a vapor which is directed to an adjacent distillation tower, operated at 900-1,000 degrees Fahrenheit. This process uses the superheated gas to release the oil from the shale, without combustion. The gas is recaptured and burned to create steam and resulting electrical power. The electrical generation process relies solely on the combustibility of the gas.

Spent Shale

The resulting waste can be ground and added to feedstocks for the production of portland cement, and the carbon dioxide is stripped and can be sold as air liquide or used to augment production in surrounding oil or gas wells.

It is the hydrogen-rich, inert environment during the heat process which (i) prevents the combustion of the valuable oils being extracted and (ii) facilitates the complete extraction of all hydrocarbons so that the spent shale is environmentally safe.

Water

Minimal amount of water will be used in start up and will be recycled within the system. The other water used in the retort process comes from the shale rock in the form of mist.

Equipment

Using conventional retort systems this technology simply interposes internal rotary and a distillation tower between the gasification plant and the power plant to make full utilization of the hot gas generated from the gasification.

Rotary Mechanism

A circuit of three rotary units inside the retort cylinder all work concurrently to (i) pre-heat the shale feedstock to 300 degrees Fahrenheit, (ii) heat the shale feed stock to 900-1,000 degrees Fahrenheit to remove the hydrocarbons in gaseous form, and (iii) cool-down the spent shale while capturing the heat loss for heating the distillation tower and/or the pre-heat cylinder. The tumbling action of the internal rotary mechanism is the most efficient means of heat transfer, as it exposes every surface of the crushed shale to the gas heat, extracting a high level of crude oil.

Distillation Tower

The distillation tower condenses the vapors of the oil extracted from the oil shale on-site and eliminates the cost of reheating oil produced at a remote location.

Hydrogenation

Hydrogenation of the oil products removes excess nitrogen. Cogeneration of electrical power occurs when the gas is recaptured and directed to the power plant where it is burned to power the generators for electricity generation.

Gas/Vapors

Vapor gas is used in the cogeneration of electricity for operation of the plant and sale into the electric grid and to heat the oil shale to 900-1,000 degrees Fahrenheit in a hydrogen-rich, inert environment. It is first directed through the rotary units to heat the oil shale.

Petroleum Products and Electricity—Oil, Light Oil and Product Gas

The gas is recaptured from the distillation tower and ignited to power the generation of electricity that is capable of firing a 300 Megawatt power generation plant. The petroleum products are fully refined ready for blending and subsequent distribution to the public. Approximately 70% of the resultant product is comprised of gasoline, diesel fuel and jet fuel.

Environmental Concerns

The spent shale is discharged absolutely devoid of hydrocarbons and other contaminants associated with earlier technologies. The technology is entirely “green” in that it emits virtually no harmful gases into the atmosphere. It obviates the thermal pollution associated with reheating the oil to 1,000 degrees Fahrenheit at another refinery location, together with the costs associated with reheating the oil for refining. The water needs are met with the moisture extracted during the pre-heating of the feedstock in the first rotary unit.

Control Philosophy

The commercial plant includes instrumentation based on the best combination of analog or computer-based controls. Capability is provided to calculate completed heat and material balances around each module and its auxiliaries and to measure energy usage, vent, and waste streams. Safety and emergency shutdown instrumentation is operable in the event of power outage. The system design maximizes the ability to add instrumentation in the field as required. Appropriate sparing is provided to ensure a 90% service factor. Provisions are included for plant winterization.

Spent Shale Cooling

The process uses minimal amount of water for cooling retorted shale. Cool recycle gas enters the base of the retort through the bottom gas distributors. The recycle gas, rising through the retorted shale, acts as a simple and compact countercurrent solids-to-gas heat exchanger; the retorted shale is cooled and the gas is heated, the reaction enhancing the thermal efficiency of the retort.

Grate Speed Controller

Retorted shale exits through the grate, passes into discharge hoppers, and leaves the retort environment through rotary seals. Purge air minimizes the escape of hydrocarbons through these rotary seals.

Retorted shale is sampled continually and a composite sample is collected during each eight-hour shift to determine retorting efficiency.

Raw-Shale Fines Storage

The raw-shale fines generation rate is assumed to be a maximum of 10% of daily mine production. Storage is provided for more than 14 million tons. The design allows permanent storage of the material in an environmentally acceptable manner and facilitates easy recovery of the material if desired.

Resource Evaluation

The determination of local technical feasibility begins with resource evaluation. Core holes at the site provide information for reserve calculations, rock strength, formation water, and fractures. Uniformity of the oil shale grade from core to core and the continuity of the oil shale deposit should establish confidence in the resource.

Oil/Gas Recovery System—Oil Separator

All gas- and oil-handling facilities have design rates equivalent to 125% of base-case operations. Each retort has its own dedicated oil/gas-handling system capable of removing oil mist from the retort off-gas with at least 99% efficiency.

Condenser

An above-bed off-gas collection system removes gas laden with oil mist from the top of each retort. The off-gas is ducted to the oil/gas-recovery system, where oil-mist droplets are removed from the off-gas by knockout drums, and electrostatic precipitators. Day-tanks are used to settle out the water from the oil to less than 1% (wt).

Recycle Gas Blower and Air Blower

Recycle gas, the portion of the mist-free off-gas that is returned to the retorts, is distributed in precisely controlled mixtures and volumes to the appropriate zones in the retort. Air and gas for the middle and upper air/gas distributors are mixed external to the retort to ensure accurate temperature control in the retorting process. Carefully designed distribution of air/gas mixtures results in efficient combustion of the residual char in the combustion zone and an even temperature profile in the upper combustion zone and retorting zone. Precise control of solids flow, gas flow, and the resultant temperature profile through the retort is the key. 

1. It is the first technology to resolve all earlier problems and issues, and render the process commercially feasible. This system extracts crude oil at 99%, refines the crude oil into petroleum products and generates electricity that can be used or sold for the general market.
 2. System attributes—extracts crude oil from shale rock, refines petroleum products, does not use external water, environmentally safe, high oil yield, less shale rock waste, generates electricity for local use and higher profit margins.
 3. This technology eliminates old issue such as—burning up profits, cost of hydrogenation, heavy tar residuals, environmental incompatibility, emissions and contaminates heavy water use and thermal pollution. 